1. Field of the Invention
This invention describes an electrically operated press tool apparatus with a hydraulic pump driven by a drive unit and which acts on a hydraulic piston cylinder unit actively connected to a roller holder, with rollers that roll on clamping jaws of a clamping pincer and thus move these relative to one another, and the press tool apparatus, apart from a pump receiver housing with a housing wall and a housing cover, includes an actuation valve for opening the passage between the pump receiver housing and the piston-cylinder unit.
2. Discussion of Related Art
Electrically operated press tool apparatus have been known for some years. Portable, hydraulically impinged press tool apparatus of the above mentioned type are applied for pressing coupling elements, such as press sleeves, press fittings, pipe muffs, tube sections pushed into one another, and likewise.
The press tools include a press unit with a clamping pincer having clamping jaws, which form a press space for receiving the coupling element to be pressed. The press pressure which is required for the pressing is provided by a hydraulic unit.
Each apparatus obtainable on the market until now, is relatively large and accordingly heavy. Reductions in the construction size have previously failed because of demands dictated the constructional shape. Changes in the size of the press pincer would limit its field of application, and accordingly the press pincer may not be knowingly reduced in size. The respective roller holder must be adapted in size to the press pincer and this also applies to the fork-like receiver, in which the press pincer is held, and which is usually manufactured as one piece with a subsequent piston-cylinder unit. The size of the cylinder housing is practically dependent on the forces to be applied, and these forces thus depend on the size of the clamping pincer.
A hydraulic unit is arranged after the piston-cylinder unit, and includes a hydraulic pump in a pump receiver housing. Hydraulic fluid, generally hydraulic oil, is pumped through high-pressure conduits from a fluid reservoir and/or from the pump receiver housing, into the hydraulic pump and from the hydraulic pump into the piston-cylinder unit. Thus, the piston is displaced in the actuation direction and the clamping pincer is closed. If such a clamping procedure is finished, then with many apparatus types, the hydraulic oil is pumped back into the hydraulic container and with some devices of this type, a direct return from the flow conduit to a return conduit or suction conduit is effected via a suitable actuation valve. The mentioned functions require a construction as described. Accordingly, a miniaturization without a loss of power is practically not possible. A reduction in size of the press pincer apparatus may only be achieved with innovative measures as a result.
In order to achieve a weight reduction of the hand-operated press tool apparatus, one has increasingly applied piston pumps, which apart from a weight saving, also achieve greater fluid pressures than gear pumps and thus may provide greater powers. The weight saving which may be achieved does not yet lead to the desired results, and the increase in the occurring fluid pressure caused new difficulties for the known press tool apparatus.
High-pressure conduits are applied within the pump receiver housing or apparatus housing of the press tools according to the state of the art, which connect the pump receiver housing, the hydraulic pump and the piston-cylinder unit to one another. German Patent Reference DE102007005837 describes a hydraulic unit of a linearly designed press tool apparatus, which is limited by an elastic wall or a flexible hose and sealingly surrounds the region of the piston pump and of a control valve. The hydraulic fluid is held in a hydraulic fluid circuit by the hydraulic fluid being led back through channels leading into a hydraulic fluid reservoir.
These high pressure conduits must seal at fluid pressures of a few hundred bars, which is often a problem. Suitable high-pressure conduits are practically only manufacturable of metal, in order to achieve the desired stability. In order to securely mount these high-pressure conduits, the pump receiver housing can be designed in a metallic manner, and the high-pressure conduits are fixed on or in the pump receiver housing. With the arrangement of the high-pressure conduits, the known pump receiver housing is often designed with a great volume in order to accommodate the components within the pump receiver housing.